Ho dimenticato di incollare lo script !!

var fade = "blendTrans(Duration=0.8)";

function showFilter(obj, visibility) {
if(ie5){
menu[obj].style.filter = fade;
menu[obj].filters[0].Apply();
menu[obj].style.visibility = visibility;
menu[obj].filters[0].Play();
}
else if(ns6){
menu[obj].style.visibility = visibility;
}
}